In many applications, such as use of the electric motor for power-assisted steering in steering systems of motor vehicles, the acoustics or the structure-borne noise produced by an electric motor constitute a significant product feature. Different types (axial, radial, tangential and/or rotary) and strengths of vibration are brought about in electric motors depending on the configuration of the electromagnetic circuit. The configuration of the electromagnetic circuit of the electric motor is primarily determined by how many slots the stator comprises, how many pole pairs the rotor comprises, the magnet technology used—for example surface magnets or pocket magnets—and the winding scheme, and always involves an acoustic compromise which promotes one of the aforementioned vibration types. Optimisation of all of the relevant vibration types by way of the electromagnetic configuration is therefore only possible to a particular extent. Conventional motor constructions generally have a rigid connection between the stator and a housing which accommodates the stator. This means that all of the vibrations which cannot be suppressed by way of the electromagnetic configuration of the electric motor are introduced directly into the housing and the machine parts positioned thereon, leading to high noise production. However, such a high noise level is unacceptable in many applications.
It is known to use structural mechanical measures, such as decoupling or damping, to optimise the vibration types or components which are not suppressed or are only partially suppressed by way of the electromagnetic configuration of the electric motor.
DE 10 2004 050 743 A1 discloses a low-vibration vacuum pump in which the motor stator is suspended in the housing of the vacuum pump by means of resilient components such as elastomer rings, leading to vibrational decoupling of the motor stator.
However, with decoupling by way of resilient parts, it is difficult to provide sufficient acoustic decoupling at the same time as sufficient fixing and centring of the stator in the motor housing.